1. Field
One embodiment of the present invention relates to a disk drive. More particularly, the invention relates to a servo-writing technique of recording product servo patterns in a disk, by using a multi spiral servo pattern.
2. Description of the Related Art
Disk drives, a representative example of which is a hard disk drive, have a disk, i.e., magnetic data-recording medium, in which servo patterns (servo data) are recorded to be used for controlling the positioning of the head (that is, for performing servo control).
The disk drive uses the servo patterns read by the read head included in the head, in order to move the head to a target position (i.e., target track) over the disk. The read head performs an operation of reading data from the target position. The head includes a write head, too, which writes data at the target position.
The servo patterns have been recorded in the disk by performing a servo-writing step during the manufacture of the disk drive. A self-servo write method attracts attention because it may increase the efficiency of the servo-writing operation. In this method, a disk having a base pattern recorded thereon is incorporated into the disk drive, and servo patterns are recorded in the disk, based on the base pattern. Thus, the self-servo write method is a method of writing servo patterns in the disk by using the disk drive is shipped as a product from the manufacturer.
In recent years, a self-servo write method has been proposed in which radial servo patterns are recorded in a disk by using a multi spiral servo patterns as a base pattern. (See, for example, U.S. Pat. Nos. 5,668,679 and 6,965,489.) The multi spiral servo pattern is composed of a plurality of spiral servo patterns (hereinafter referred to as spiral patterns, in some cases).
The radial servo patterns are product servo patterns that constitute concentric servo tracks. The term “product servo pattern” means servo patterns that are used to control the positioning of the head after the disk drive has been shipped as a product. (Hereinafter, the radial servo patterns will be referred to as final patterns, in some cases.)
Each of the spiral patterns constituting the multi spiral servo pattern contains only servo-burst data and a sync mark, from which a position-error signal may be reproduced. The disk drive uses the multi spiral servo pattern exclusively for head tracking (namely, for positioning the head).
The multi spiral servo pattern may be used not only for tracking the head, but also for generating sector addresses that are required in recording the product servo patters (final patterns). Then, a self-servo write method can be performed, in which the multi spiral servo pattern is effectively utilized.